This invention relates to programmable logic devices (“PLDs”), and more particularly to inclusion of high-speed serial interface circuitry in PLDs.
PLDs are relatively general-purpose devices that are manufactured to meet the various needs of many different potential users. The broader the range of needs that a PLD can satisfy, the larger the potential market for the PLD. A large volume of sales helps to hold down or reduce the unit cost of the PLD. Of course, adding more features to the PLD puts upward pressure on unit cost. So there is a trade-off between giving the PLD too few features to make it widely marketable, and giving it so many features that it becomes too expensive.
An area of recent interest in PLD design is the inclusion of high-speed serial interface (“HSSI”) circuitry. Different users may want to use HSSI circuitry in many different ways. For example, there are many different industry-standard protocols for high-speed serial communication (“HSSC”). A user may want to use any of those industry-standard protocols. Or a user may want to use the user's own custom protocol.
Typically what is done in HSSC is to send and/or receive one or more channels or lanes of high-speed serial data. For example, each channel may operate in the gigahertz range (i.e., at a data rate in the range from approaching 1 GHz to several GHz). (Particular frequencies mentioned herein are only illustrative, and the invention is equally applicable to other lower or higher frequencies.) Some users may want to use one or more HSSI transmitter and/or receiver channels individually. Other users may want to use multiple HSSI transmitter and/or receiver channels in parallel (e.g., four channels operating together, eight channels operating together, etc.). “Operating together” typically means that there is some synchronization among the channels thus operating together. A user of channels operating together may want to use multiple instances of such channel groups.
To support such a wide range of possible HSSI use, a substantial amount of HSSI circuitry may need to be included on a PLD. And because of the possible need for synchronization among some or all of the channels of such HSSI circuitry, it may be preferable to provide this circuitry in a concentrated area or location on the PLD. Accommodating such a large amount of HSSI circuitry in a concentrated area may warrant innovative modifications to known PLD architectures.